Power factor correction circuit and power supply including the same

ABSTRACT

There are provided a power factor correction circuit, and a power supply including the same, the power factor correction circuit including a main switch adjusting a phase difference between a current and a voltage of input power, a main inductor storing or discharging the power according to switching of the main switch, a snubber circuit unit including a snubber switch forming a transfer path for surplus power present before the main switch is turned on and a snubber inductor adjusting an amount of a current applied to the snubber switch, and a reduction circuit unit including an auxiliary inductor inductively coupled to the snubber inductor and an auxiliary resistor consuming power induced from the snubber inductor through the auxiliary inductor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2012-0143965 filed on Dec. 11, 2012, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power factor correction circuit and apower supply including the same.

2. Description of the Related Art

Recently, the governments of many countries have recommended theefficient use of energy according to energy efficiency policies, and inparticular, the implementation of efficient energy usage in electronicproducts and home appliances is widely recommended.

In efficiently using energy according to such a governmentalrecommendation, a correction circuit for implementing efficient energyusage is largely applied to a power supply device that supplies power toelectronic products, home appliances, and the like.

A power factor correction circuit is an example of the correctioncircuit. The power factor correction circuit is a circuit that switchesinput power to adjust a phase difference (power factor) between acurrent and a voltage of the input power in such a manner that power iseffectively transferred to a rear stage.

However, when this power factor correction circuit performs a switchingoperation in order to adjust the phase difference of the input power, apeak voltage may be generated, such that a switching element may bedamaged and switching loss may occur.

Patent Document 1, the following related art document, relates to apower factor improvement circuit for improving a power factor usingenergy accumulated in an inductor of a snubber circuit unit, but doesnot disclose a technical point for decreasing a spike voltage generatedduring switching.

RELATED ART DOCUMENT

(Patent Document 1) US Patent Laid-Open Publication No. 2011/0199066

SUMMARY OF THE INVENTION

An aspect of the present invention provides a power factor correctioncircuit capable of decreasing a peak voltage generated at the time atwhich a snubber switch providing a zero-voltage turn-on condition to amain switch switching input power to improve a power factor thereof isturned off, and a power supply including the same.

According to an aspect of the present invention, there is provided apower factor correction circuit, including: a main switch adjusting aphase difference between a current and a voltage of input power; a maininductor storing or discharging the power according to switching of themain switch; a snubber circuit unit including a snubber switch forming atransfer path for surplus power present before the main switch is turnedon and a snubber inductor adjusting an amount of a current applied tothe snubber switch; and a reduction circuit unit including an auxiliaryinductor inductively coupled to the snubber inductor and an auxiliaryresistor consuming power induced from the snubber inductor through theauxiliary inductor.

The auxiliary inductor may be inductively coupled to the main inductorto transfer the power induced from the snubber inductor to the maininductor, and the auxiliary resistor may consume the power induced fromthe main inductor through the auxiliary inductor.

The snubber inductor may be inductively coupled to the main inductor totransfer the power to the main inductor.

The auxiliary resistor may detect the power induced through theauxiliary inductor as a current.

The snubber switch may be turned on for a preset first time, and themain switch may be turned on after a preset first delay time has elapsedfrom a time at which the snubber switch is turned on.

The first time may be longer than the first delay time.

The power factor correction circuit may further include a reversecurrent preventing diode preventing a reverse current of the mainswitch.

The power factor correction circuit may further include a diodeproviding a transfer path for the power released from the main inductoraccording to the switching of the main switch.

The power factor correction circuit may further include a controllerproviding switching control signals controlling switching operations ofthe main switch and the snubber switch.

The input power may be rectified power.

The main inductor, the snubber inductor, and the auxiliary inductor maybe formed in a single magnetic core.

According to another aspect of the present invention, there is provideda power supply, including: a power factor correction circuit including amain switch adjusting a phase difference between a current and a voltageof input power; a main inductor storing or discharging the poweraccording to a switching operation of the main switch; a snubber circuitunit including a snubber switch forming a transfer path for surpluspower present before the main switch is turned on and a snubber inductoradjusting an amount of a current applied to the snubber switch; and areduction circuit unit including an auxiliary inductor inductivelycoupled to the snubber inductor and an auxiliary resistor consumingpower induced from the snubber inductor through the auxiliary inductor;a power converting unit switching the power from the power factorcorrection circuit to convert the power into power having a presetlevel; and a switching controlling unit controlling the switching of thepower performed by the power converting unit.

The auxiliary inductor may be inductively coupled to the main inductorto transfer the power induced from the snubber inductor to the maininductor, and the auxiliary resistor may consume the power induced fromthe main inductor through the auxiliary inductor.

The snubber inductor may be inductively coupled to the main inductor totransfer the power to the main inductor.

The auxiliary resistor may detect the power induced through theauxiliary inductor as a current.

The snubber switch may be turned on for a preset first time, and themain switch may be turned on after a preset first delay time has elapsedfrom a time at which the snubber switch is turned on.

The first time may be longer than the first delay time.

The power factor correction circuit may further include a reversecurrent preventing diode preventing a reverse current of the mainswitch.

The power factor correction circuit may further include a diodeproviding a transfer path for the power released from the main inductoraccording to the switching of the main switch.

The power factor correction circuit may further include a capacitorstabilizing the power transferred from the diode.

The power factor correction circuit may further include a controllerproviding switching control signals controlling switching operations ofthe main switch and the snubber switch.

The power supply may further include a rectifying unit transferring theinput power generated by rectifying alternating current (AC) power tothe power factor correction circuit.

The main inductor, the snubber inductor, and the auxiliary inductor maybe formed in a single magnetic core.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1 and 2 are circuit views schematically showing a power factorcorrection circuit according to an embodiment of the present invention;

FIG. 3 is a graph illustrating switching control signals of a mainswitch and a snubber switch employed in the power factor correctioncircuit according to the embodiment of the present invention;

FIG. 4 is an enlarged view of part A of FIG. 3;

FIGS. 5A and 5B are graphs respectively showing voltage generated acrossthe snubber switch employed in the power factor correction circuitaccording to the embodiment of the present invention; and

FIG. 6 is a view schematically showing a configuration of a power supplyincluding a power factor correction circuit according to an embodimentof the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the shapes and dimensions ofelements may be exaggerated for clarity, and the same reference numeralswill be used throughout to designate the same or like elements.

FIGS. 1 and 2 are circuit views schematically showing a power factorcorrection circuit 100 according to an embodiment of the presentinvention.

Referring to FIG. 1, the power factor correction circuit 100 accordingto the embodiment of the present invention may include a main inductorL, a main switch S, a snubber circuit unit 110, and a reduction circuitunit 120, and may further include a diode D, a capacitor C, a reversecurrent preventing diode DR, and a controller 130.

The main switch S may perform a switching operation to adjust a phasedifference between a voltage and a current of input power input from aninput terminal IN. Here, the input power may be rectified power.

The reverse current preventing diode DR may prevent a reverse current ofthe main switch S by providing a bypass path from an anode to a cathodeof the reverse current preventing diode DR, when the reverse current isapplied to the main switch S. When the main switch S is configured of atransistor, the reverse current preventing diode DR may be a diodeformed in a body of the transistor. However, the reverse currentpreventing diode DR is not limited thereto and may be a separate diode.

The main inductor L may be disposed between the input terminal INreceiving the input power and the main switch S to thereby store orrelease the power according to the switching operation of the mainswitch S and the diode D may provide a transfer path for the powerreleased from the main inductor L according to the switching operationof the main switch S. In addition, the capacitor C may be connected toan output terminal OUT in parallel to thereby stabilize the power outputfrom the diode D.

The snubber circuit unit 110 may include a snubber switch Sn connectedto the main switch in parallel and a snubber inductor Ln providedbetween the snubber switch Sn and the main switch S to adjust an amountof a current flowing in the snubber switch Sn.

The controller 130 may generate switching control signals G and Gncontrolling switching operations of the main switch S and the snubberswitch Sn.

The main switch S and the snubber switch Sn according to the embodimentof the present invention may be configured of one of an insulated gatebipolar transistor (IGBT), a metal oxide semiconductor field-effecttransistor (MOS-FET) and a bipolar junction transistor (BJT). Referringto FIG. 2, although FIG. 2 shows an example in which the main switch Sand the snubber switch Sn are configured of the BJTs, the presentinvention is not limited thereto.

FIG. 3 is a graph illustrating switching control signals of the mainswitch S and the snubber switch Sn employed in the power factorcorrection circuit 100 according to the embodiment of the presentinvention and FIG. 4 is an enlarged view of part A of FIG. 3. In thecase in which the switching control signals G and Gn are at high levels,the main switch S and the snubber switch Sn are turned on and in thecase in which the switching control signals G and Gn are at low levels,the main switch S and the snubber switch Sn are turned off.

The main switch S of the power factor correction circuit 100 accordingto the embodiment of the present invention may perform the switchingoperation to adjust the phase difference between the voltage and thecurrent of the input power, thereby improving the power factor of theinput power. In this case, the snubber switch Sn may bypass surpluspower remaining during on and off switching of the main switch S to aground, whereby a zero-voltage switching condition may be provided tothe main switch S. Therefore, switching loss of the main switch S may beremoved.

As shown in FIGS. 3 and 4, the snubber switch Sn is turned on earlierthan the main switch S by a first delay time TD1, thereby forming atransfer path for the surplus power. Here, the snubber switch Sn may beturned on for a first time T1. In this case, the first time T1 is set tobe longer than the first delay time TD1, such that the snubber switch Snmay be turned off before the main switch S is turned off.

Meanwhile, when the snubber switch Sn is turned on, in order to preventthe current having a high current level from being applied to thesnubber switch Sn, the snubber inductor Ln is provided between thesnubber switch Sn and the main switch S. In this configuration, when thesnubber switch Sn is turned off, since a path through which the currentflowing in the snubber inductor Ln is conducted is not present, a peakvoltage is generated across the snubber switch Sn, whereby damage to thesnubber switch Sn and switching loss thereof may occur.

FIGS. 5A and 5B are graphs respectively showing voltage generated acrossthe snubber switch Sn employed in the power factor correction circuitaccording to the embodiment of the present invention. FIG. 5A is a graphshowing the voltage generated across the snubber switch Sn when the paththrough which the current flowing in the snubber inductor Ln isconducted is not present, during the turning off of the snubber switchSn.

Before the first time t1, the snubber switch Sn may be turned off, suchthat a high voltage is generated across the snubber switch Sn.Thereafter, at the first time t1, the snubber switch Sn is turned on,such that a low voltage is generated across the snubber switch Sn.However, at a time t2, when the snubber switch Sn is turned on, sincethe path through which the current flowing in the snubber inductor Ln isconducted is not present, a high peak voltage is generated.

In order to reduce the peak voltage, referring to FIG. 1, the powerfactor correction circuit may employ the reduction circuit unit 120.

The reduction circuit unit 120 may include an auxiliary inductor Laelectromagnetically inductively coupled to the snubber inductor Ln andan auxiliary resistor Ra consuming power induced through the auxiliaryinductor La. The auxiliary inductor La is inductively coupled to thesnubber inductor Ln to receive the current flowing in the snubberinductor Ln as the power during the turning-off the snubber switch Sn,thereby providing a path for the current.

In addition, the auxiliary inductor La may be electromagneticallyinductively coupled to the main inductor L to thereby transfer the powerinduced from the snubber inductor Ln to the main inductor L. Here, asshown in FIG. 1, the snubber inductor Ln and the auxiliary inductor Laare inductively coupled to each other in a harmony mode (dots aredisposed in the same direction), and the auxiliary inductor La and themain inductor L are inductively coupled to each other in a differentialmode (dots are disposed in opposite directions), such that the powertransferred from the snubber inductor Ln to the main inductor L throughthe auxiliary inductor La may be recycled. That is, a part of the powertransferred from the snubber inductor Ln may be transferred to thereduction circuit unit 120 and consumed by the auxiliary resistor Ra,and another part of the power transferred from the snubber inductor Lnmay be transferred to the main inductor L to be recycled.

In addition, the snubber inductor Ln according to the embodiment of thepresent invention may not only transfer power to the main inductor Lthrough the auxiliary inductor La, but also directly transfer the powerto the main inductor L by being inductively coupled to the main inductorL.

The main inductor L, the snubber inductor Ln, and the auxiliary inductorLa according to the embodiment of the present invention may be formed ina single magnetic core. That is, the main inductor L, the snubberinductor Ln, and the auxiliary inductor La may share a single core. Inthis case, an inductor mounted space and cost may be saved.

In addition, in a section in which the snubber switch Sn is turned off,since the snubber inductor Ln is opened and thus, is not coupled to themain inductor L and the auxiliary inductor La, the auxiliary inductor Lareceives the power from the main inductor L. In this case, the auxiliaryresistor Ra may measure the current flowing in the main inductor L. Thatis, the auxiliary resistor Ra may be operated as a current sensor.Therefore, an external current sensor may be removed, whereby a cost anda mounting area of the entire power factor correction circuit may bedecreased.

FIG. 5B is a graph showing the voltage generated across the snubberswitch Sn when the path through which the current flowing in the snubberinductor Ln is conducted is present, during the turning off of thesnubber switch Sn. Comparing FIGS. 5A and 5B, it may be appreciated thatthe peak voltage is reduced at the time t2.

FIG. 6 is a view schematically showing a configuration of a power supplyincluding the power factor correction circuit 100 according to anembodiment of the present invention.

Referring to FIG. 6, the power supply may include the power factorcorrection circuit 100, a power converting unit 200, a switchingcontrolling unit 300, and a rectifying unit 400.

The power factor correction circuit 100 of FIG. 6 is the same as thepower factor correction circuit 100 shown in FIG. 1. Therefore, adetailed description thereof will be omitted.

The power converting unit 200 may switch direct current (DC) power fromthe power factor correction circuit to convert the DC power into DCpower having a preset voltage level and then supply the converted DCpower to a load, the switching controlling unit 300 may control theswitching of the power converting unit 200 according to a voltage orcurrent level of the output DC power, and the rectifying unit 400 maytransfer the input power generated by rectifying alternating current(AC) power to the power factor correction circuit 100.

As set forth above, according to the embodiment of the presentinvention, the zero-voltage turn-on condition is provided to the mainswitch switching the input power to improve the power factor thereof,whereby damage to the main switch may be prevented and switching lossthereof may be decreased.

In addition, the peak voltage that may be generated across the snubberswitch providing the zero-voltage turn-on condition to the main switchis transferred to the main inductor through power coupling, wherebydamage to the snubber switch may be prevented and power recycle may bemay be allowed.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

1. A power factor correction circuit, comprising: a main switchadjusting a phase difference between a current and a voltage of inputpower; a main inductor storing or discharging the power according toswitching of the main switch; a snubber circuit unit including a snubberswitch forming a transfer path for surplus power present before the mainswitch is turned on and a snubber inductor adjusting an amount of acurrent applied to the snubber switch; and a reduction circuit unitincluding an auxiliary inductor inductively coupled to the snubberinductor and an auxiliary resistor consuming power induced from thesnubber inductor through the auxiliary inductor, wherein the auxiliaryinductor is inductively coupled to the main inductor to transfer thepower induced from the snubber inductor to the main inductor, and theauxiliary resistor consumes the power induced from the main inductorthrough the auxiliary inductor.
 2. (canceled)
 3. The power factorcorrection circuit of claim 1, wherein the snubber inductor isinductively coupled to the main inductor to transfer the power to themain inductor.
 4. The power factor correction circuit of claim 1,wherein the auxiliary resistor detects the power induced through theauxiliary inductor as a current.
 5. The power factor correction circuitof claim 1, wherein the snubber switch is turned on for a preset firsttime, and the main switch is turned on after a preset first delay timehas elapsed from a time at which the snubber switch is turned on.
 6. Thepower factor correction circuit of claim 5, wherein the preset firsttime is longer than the preset first delay time.
 7. The power factorcorrection circuit of claim 1, further comprising a reverse currentpreventing diode preventing a reverse current of the main switch.
 8. Thepower factor correction circuit of claim 1, further comprising a diodeproviding a transfer path for the power released from the main inductoraccording to the switching of the main switch.
 9. The power factorcorrection circuit of claim 8, further comprising a capacitorstabilizing the power transferred from the diode.
 10. The power factorcorrection circuit of claim 1, further comprising a controller providingswitching control signals controlling switching operations of the mainswitch and the snubber switch.
 11. The power factor correction circuitof claim 1, wherein the input power is rectified power.
 12. The powerfactor correction circuit of claim 1, wherein the main inductor, thesnubber inductor, and the auxiliary inductor are formed in a singlemagnetic core.
 13. A power supply, comprising: a power factor correctioncircuit including a main switch adjusting a phase difference between acurrent and a voltage of input power; a main inductor storing ordischarging the power according to a switching operation of the mainswitch; a snubber circuit unit including a snubber switch forming atransfer path for surplus power present before the main switch is turnedon and a snubber inductor adjusting an amount of a current applied tothe snubber switch; and a reduction circuit unit including an auxiliaryinductor inductively coupled to the snubber inductor and an auxiliaryresistor consuming power induced from the snubber inductor through theauxiliary inductor; a power converting unit switching the power from thepower factor correction circuit to convert the power into power having apreset level; and a switching controlling unit controlling the switchingof the power performed by the power converting unit, wherein theauxiliary inductor is inductively coupled to the main inductor totransfer the power induced from the snubber inductor to the maininductor, and the auxiliary resistor consumes the power induced from themain inductor through the auxiliary inductor.
 14. (canceled)
 15. Thepower supply of claim 13, wherein the snubber inductor is inductivelycoupled to the main inductor to transfer the power to the main inductor.16. The power supply of claim 13, wherein the auxiliary resistor detectsthe power induced through the auxiliary inductor as a current.
 17. Thepower supply of claim 13, wherein the snubber switch is turned on for apreset first time, and the main switch is turned on after a preset firstdelay time has elapsed from a time at which the snubber switch is turnedon.
 18. The power supply of claim 17, wherein the preset first time islonger than the preset first delay time.
 19. The power supply of claim13, wherein the power factor correction circuit further includes areverse current preventing diode preventing a reverse current of themain switch.
 20. The power supply of claim 13, wherein the power factorcorrection circuit further includes a diode providing a transfer pathfor the power released from the main inductor according to the switchingof the main switch.
 21. The power supply of claim 20, wherein the powerfactor correction circuit further includes a capacitor stabilizing thepower transferred from the diode.
 22. The power supply of claim 13,wherein the power factor correction circuit further includes acontroller providing switching control signals controlling switchingoperations of the main switch and the snubber switch.
 23. The powersupply of claim 13, further comprising a rectifying unit transferringthe input power generated by rectifying alternating current (AC) powerto the power factor correction circuit.
 24. The power supply of claim13, wherein the main inductor, the snubber inductor, and the auxiliaryinductor are formed in a single magnetic core.
 25. The power factorcorrection circuit of claim 1, wherein the auxiliary resistor of thereduction circuit unit is coupled in series with the auxiliary inductorto consume power induced from the snubber inductor and from the maininductor through the auxiliary inductor.
 26. The power supply of claim13, wherein the auxiliary resistor of the reduction circuit unit iscoupled in series with the auxiliary inductor to consume power inducedfrom the snubber inductor and from the main inductor through theauxiliary inductor.